Process and device for electric spot welding

#This application is a United States National Phase application of International Application PCT/EP2005/013946 and claims the benefit of priority under 35 U.S.C. §119 of DE 10 2005 001 341 filed, 11 Jan. 2005 the entire contents of which are incorporated herein by reference.

#The present invention pertains to a process and a device for the electric spot welding of a plurality of welding spots made along a path of a workpiece by means of welding guns with electrodes. The workpiece and the welding guns are moved by a displacing motion between the welding spots by one or more multiaxial robots, especially articulated arm robots.

#Such a spot welding technique with electric spot welding guns, e.g., C tongs or X tongs, is known from practice. A plurality of welding spots are made with this welding technique one after another along a path on the workpiece, especially a vehicle body part. The workpiece and the welding guns are moved relative to one another by one or more multiaxial robots, especially in the form of six-axis articulated arm robots. In one variant, the robot guides the welding guns in relation to the stationary workpiece. In the second variant, the robot moves the workpiece in relation to the stationary welding guns. In a third variant, both the welding guns and the workpiece can be moved relative to one another by a robot each. A displacing motion is performed during this relative motion between the workpiece and the welding guns along the path to approach the individual welding positions. In the state of the art, the workpiece and the welding guns are positioned relative to one another at the weld joint, and an inoperative position without further displacing motion is then assumed. When the welding guns are closed and during the welding process, the relative positions of the welding guns and the workpiece are preserved. The robot or robots holding the welding guns and/or the workpiece stop while the welding is performed. After the welding is finished, then the robot or robots relatively move the workpiece and welding guns to the next position. This process is then repeated for each new welding position.

#In the drawings:

#FIG. 1 is a schematic side view of a welding means with robots, spot welding guns and a workpiece;

#FIGS. 2 and 3 are a side view and top view, respectively, of a step by step process of electrodes and tong arms during the making of a plurality of welding spots along a straight path;

#Referring to the drawings in particular, the present invention pertains to a process for the electric spot welding of workpieces 2 as well as to a correspondingly controlled welding means 1 used herefor, which contains a correspondingly suitable control 4 and a control program.

#FIG. 1 shows the side view of a schematic embodiment of such a welding means 1. The welding means 1 comprises welding guns 10 for electric spot welding and a robot 3 with a control 4, which robot guides the welding guns 10 in the exemplary embodiment being shown relative to a workpiece 2 shown in a cutaway view. A plurality of welding spots 15 are made here with the welding guns 10 along a path 16 on the workpiece 2. The welding guns 10 are moved by the robot 3 from welding spot 15 to welding spot 15 in a displacing motion.

#The workpiece 2 may be of any type, size and design. The workpiece is preferably a component of vehicle body shells. For example, two components are connected to one another at a projecting flange by means of welding spots 15. The path 16 or sequence of welding spots 15 to be made on the workpiece 2 is determined by the geometry of the component. The path 16 may have a straight and flat course in the simplest form, as in FIGS. 2 and 3. On the other hand, it may have any other desired share and, e.g., the curved shape shown in FIG. 4. FIG. 4 illustrates, for example, a component opening located on the inside, e.g., a door opening of a body, on the peripheral edge of which the welding spots 15 are to be made.